Igor Poltinnikov, Presenter: Nothing to Disclose

Kevin Fallon, Abstract Co-Author: Nothing to Disclose

Ying Xioa, Abstract Co-Author: Nothing to Disclose

Jay E. Reiff PhD, Abstract Co-Author: Nothing to Disclose

Walter J. Curran MD, Abstract Co-Author: Nothing to Disclose

Maria Werner-Wasik MD, Abstract Co-Author: Nothing to Disclose

Purpose/Objective: To evaluate dosimetric predictors of acute esophagitis (AE) and clinical outcome of patients (pts) with non-small cell lung cancer (NSCLC) receiving reirradiation with hypofractionated three-dimensional (3D) radiation therapy (RT) while immobilized in Stereotactic Body Frame (SBF). Materials/Methods: Records of 18 pts with NSCLC who have received a hypofractionated reirradiation to the lung tumors / mediastinum, while immobilized in SBF, were reviewed to assess the safety and efficacy of treatment. Immediately prior to each treatment, a CT scan was obtained, and the isocenter was chosen by comparing anatomical landmarks from the planning scan to the pretreatment CT study. Pts, while in the SBF, were then transported in the treatment position on a modified stretcher with a smooth surface to minimize patient (pt) displacement. Treatment planning involved CT simulation in all cases, and hypofractionated RT was used. Esophagus was contoured on each 1.5 mm thick CT slice. Two axial segments of esophagus merged together were viewed as esophagus disc (ED). For each ED, the percentage (%) of the volume (V) of esophageal circumference treated to % of prescribed dose (PD) was assessed. Number of esophagus discs (EDs) with 50 % V or any % V of circumference receiving more than or equal to (≥) 50 %, 80 %, and 100 % of PD (50 % V ≥ 50 % PD; 50 % V ≥ 80 % PD; any % V ≥ 100 % PD) was calculated. The length of the esophagus within a treatment port and dosimetric variables addressing circumferential and longitudinal coverage of esophagus were correlated with AE using exact Wilcoxon test. Results: The SBF immobilization was well tolerated by most pts. Two pts could not complete the prescribed course of treatment due to general deterioration. A median of 6 RT fields (range: 3 - 8) was used per pt. A median dose was 32 Gy (range: 4 - 42) with a median fraction size of 4 Gy (2.5-4.2) delivered 3-5 times per week. Dose was prescribed to a median isodose line of 90 % (range: 80-95). Presenting symptoms resolved completely or partially in 11 pts and were unchanged in 7 pts. Follow-up imaging demonstrated complete response in 1 pt, partial response in 4 pts, stable disease in 5 pts and disease progression in 8 pts prior to death or at the time of last follow-up visit. Median survival time from the start of reirradiation in SBF till death was 5.5 months (range: 2.5 - 30). One pt with history of pneumonectomy developed grade 2 radiation pneumonitis. Grade 1 and grade 2 AE were observed in 3 and 4 pts accordingly; in all 7 pts symptoms disappeared within 3 months of RT completion. No grade 3 or higher events were observed. Only 2 out of 5 pts treated with concurrent chemotherapy developed AE. By applying exact Wilcoxon test analysis, the length of the esophagus within a treatment port did not predict for AE (p = 0.71). However, the increasing number of EDs predicted for AE for the following isodose coverage of esophageal circumference: 50 % V ≥ 50 % PD (p = 0.023), 50 % V ≥ 80 % PD (p = 0.047) and any % V ≥ 100 % PD (p = 0.004). The general observation shows that pts with at least 2 EDs receiving ≥ 100 % PD to any V of circumference had AE compared to those with zero EDs. Conclusions: Reirradiation using hypofractionated 3D RT, CT-based isocenter verification and SBF immobilization is a safe and effective strategy for palliation of symptoms and tumor control in selected pts with recurrent NSCLC. Low-grade AE is the most common toxicity associated with reirradiation. The length of esophagus in the RT field does not predict for AE. However, increasing number of EDs displaying the combination of longitudinal and circumferential 3D dose distribution along esophagus is a valuable predictor for AE. While evaluating 3D RT plans for NSCLC, attempts should be made to apply 50 % of prescribed dose to less than half of esophageal circumference and avoid including any volume of esophageal circumference in the full prescribed dose region.

Poltinnikov, I, Fallon, K, Xioa, Y, Reiff, J, Curran, W, Werner-Wasik, M, Combination of Longitudinal and Circumferential Three-dimensional Esophageal Dose Distribution Predicts Acute Esophagitis in Hypofractionated Reirradiation of Patients with Non-Small-Cell Lung Cancer Treated in Stereotactic Body Frame.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4417854.html